American Catholic places the rise of the United States' political conservatism in the context of ferment within the Roman Catholic Church. How did Roman Catholics shift from being perceived as un-American to emerging as the most vocal defenders of the United States as the standard bearer in world history for political liberty and economic prosperity? D. G. Hart charts the development of the complex relationship between Roman Catholicism and American conservatism, and shows how these two seemingly antagonistic ideological groups became intertwined in advancing a certain brand of domestic and international politics.

Contrary to the standard narrative, Roman Catholics were some of the most assertive political conservatives directly after World War II, and their brand of politics became one of the most influential means by which Roman Catholicism came to terms with American secular society. It did so precisely as bishops determined the church needed to update its teaching about its place in the modern world. Catholics grappled with political conservatism long before the supposed rightward turn at the time of the Roe v. Wade decision in 1973.

Hart follows the course of political conservatism from John F. Kennedy, the first and only Roman Catholic president of the United States, to George W. Bush, and describes the evolution of the church and its influence on American politics. By tracing the roots of Roman Catholic politicism in American culture, Hart argues that Roman Catholicism's adaptation to the modern world, whether in the United States or worldwide, was as remarkable as its achievement remains uncertain. In the case of Roman Catholicism, the effects of religion on American politics and political conservatism are indisputable.